Surface penetrating radar, also referred to as ground penetrating radar (GPR), is used to investigate the surface and subsurface features of a target zone or area. In general, GPR uses transmitting and receiving antennas, or only one antenna containing both functions. The transmitting antenna typically radiates short pulses of high-frequency radio waves into the ground. When the wave hits a buried object or a boundary with different electromagnetic properties, the wave is reflected from the object or boundary, and a receiving antenna records the reflected return signal. The return signals can be used to locate and/or construct an image of what is underground because the return signals will vary depending on the depth and composition of buried objects.
There are many applications for GPR in a number of fields. For example, GPR is used in the Earth sciences to study bedrock, soils, groundwater, and ice. Engineering applications include nondestructive testing (NDT) of structures and pavements, locating buried structures and utility lines, and studying soils and bedrock. In environmental remediation, GPR is used to define landfills, contaminant plumes, and other remediation sites, while in archaeology it is used for mapping archaeological features and cemeteries. GPR is used in law enforcement for locating clandestine graves and buried evidence, and military uses include detection of buried mines and unexploded ordnance as well as subterranean tunnels and fortifications.
Aerial or airborne GPR systems are advantageous in regions where direct contact with the ground is impossible or dangerous, and/or in regions where non-invasive radar imaging is to take place. Existing airborne GPR systems are broad band, complex, heavy, and require large and expensive to operate aircraft to carry the GPR systems. Additionally, the wide bandwidth of conventional GPR systems can cause distortion, i.e., frequency dependent attenuation, and dispersion, i.e., frequency dependent velocity, which can greatly limit the penetration distance and reflection time resolution. Thus, systems that achieve improved penetration distance and reflected signal recovery, while concurrently achieving reduced cost, size, and weight are needed so that ground penetrating radar can be more extensively and usefully employed.